The present invention relates to a storage system comprising a plurality of control units each connected with a plurality of disk units.
In recent years, demand has risen to shorten the time required for the process (hereinafter referred to as the backup process) to replicate the data stored in a given storage unit to another storage unit held by a business organization. On the background of this demand is the increase in the information amount held by each organization, and the time consumed for backup is ever on the increase, while the increase in the business hours of each organization has decreased the relative length of time that can be assigned to the backup process.
A “snapshot” has been proposed in JP-A-7-210439 and JP-A-2001-318833 as a technique for backing up the data stored in a storage device without suspending the routine work of organizations. The snapshot is defined as a function of producing a copy of a storage area of a storage device at a specific time point without the intermediary of the computer connected with the storage device. Taking advantage of the function, the user uses the original storage area for business, and the data stored in the copy storage area for backup.